(1) Field of the Invention
The present invention relates generally to a test method for characterizing potentially explosive materials, and more particularly a test method that simulates a large scale test of explosive materials while only employing very small quantities of materials for the characterization.
(2) Description of the Prior Art
U.S. Pat. No. 6,669,753, assigned to the Government of the United States of America, teaches that a small-scale reactivity test (i.e. SSRT) can measure the shock reactivity of explosive materials. The SSRT, as originally configured, consisted of four detonators in four separate holes in a steel confinement apparatus bonded to an aluminum dent block. In the example, ammonium nitrate formulations that have various levels of shock resistance are placed in the steel holes between the detonator and the aluminum dent block. Explosive performance is gauged by measuring the dent depth produced in the aluminum dent block.
While the related art test is useful for determining the prompt shock reaction of various explosive materials, it fails to quantify the total energy available to internal blast that also includes delayed shock reaction and combustion of remaining reactants with the air. The selection of the detonator can influence the results of the test. That is some detonators are encapsulated in polymeric materials that can burn, while in other detonators the detonating materials are encapsulated in non-organic materials that have a lower level of heat contribution. The contribution of the detonator is particularly important when evaluating the total output of a small scale explosive event, because unlike a large scale test where the contribution of the detonator is relatively small, the detonator material in a small test can account for a significant portion of the total explosive material. For example, in a large-scale test the explosive material weighs 23 Kg, whereas in an SSRT the explosive material is under 0.5 grams. In both tests, the detonator, such as RP-80, has 80 mg of PETN and 123 mg of RDX. In the large-scale test the detonator explosives would account for only ˜9×10−5% of the total, but in the small scale test the detonator explosives account for 40% or more.
Although related conventional art discusses a small scale reactivity test using conventional technology based on detonators containing polymeric materials, a small scale reactivity test is needed that measures not only shock sensitivity and reactivity, but also any ancillary reactions that occur in addition to the shock reaction, where the tests takes into account factors that are an artifact of the small scale of the test. Furthermore, while the SSRT measures the substantially instantaneous reaction, it does not measure the internal blast reaction, that is the total reaction. Unburned materials and gases given off by the initial reaction create a second slower burning reaction using the ambient oxygen, and this second reaction contributes to the internal blast reaction. The sum of the shock reactivity reaction (the fast reaction) and the post reaction (which is substantially a slower reaction) constitutes the total reaction. (e.g., the internal blast reaction). Further, a test is needed to resolve the total reaction into its component reactions.